1. Field of the Invention
The present invention relates to a fundus camera for performing observation using a near-infrared light and performing color photographing and fluorescence photographing such as fundus autofluorescence (FAF) photographing.
2. Description of the Related Art
As an example of the fundus camera for observing and photographing the fundus, there are a mydriatic fundus camera, in which a mydriatic agent is instilled into an eye, and a non-mydriatic fundus camera, in which a mydriatic agent is not instilled into an eye.
In general, the mydriatic fundus camera is mainly used by an ophthalmologist. The mydriatic fundus camera is suitable for taking a plurality of photographs by using various photographing techniques such as the color photographing, the fluorescence photographing, and the specialized filter photographing. On the other hand, the non-mydriatic fundus camera is mainly used for a group medical examination or by an internist. The non-mydriatic fundus camera is suitable for taking a single photograph. However, the ophthalmologist may also practice the medical examination without the instillation of the mydriatic agent, so that a burden on a person to be examined can be reduced. Therefore, the non-mydriatic photographing has been demanded.
Japanese Patent No. 2000-300521 discusses a non-mydriatic fundus camera capable of performing observation using a near-infrared light and performing color photographing and visible fluorescence (FA) photographing. In the fundus camera, a visible light cut-off filter is disposed in a fundus illumination system to be insertable/removable, and a visible light observing unit such as an optical finder, and two image capture units for a near-infrared observing, and for photographing a still image, are disposed in a photographing system.
When the FA photographing is performed by using the fundus camera discussed in Japanese Patent No. 2000-300521, until a fluorescent light appears, the visible light cut-off filter is disposed outside the optical path, and the observation is performed through the finder. When the fluorescent light appears, the visible light cut-off filter is inserted into the optical path to allow the near-infrared light to illuminate the eye to be examined. The fundus image is observed through an observation image capture unit capable of performing the observation of a moving image.
In addition, at the time of photographing, the optical path is switched by a flip-up mirror, so that the photographing is performed. In addition, it is important that the exciter filter and the barrier filter used for the visible fluorescence photographing have a characteristic of transmitting the near-infrared light.
In addition, recently, the autofluorescence photographing has attracted attention as a new method of diagnosis for age-related macular degeneration (AMD). The autofluorescence was used for a laser scan opthalmoscopic apparatus in the early stage, but the autofluorescence has also been used for the fundus camera in these days.
When the autofluorescence photographing is performed by using the fundus camera, an exciter filter is inserted into a fundus illumination system, and an examiner performs the observation of the fundus of the eye to be examined and alignment by using a visible light. In addition, at the time of fluorescence photographing, a barrier filter is inserted into a photographing system in synchronization with the photographing, and the photographing is performed.
Conventionally, similar to a first conventional fundus camera illustrated in FIG. 4, in the mydriatic fundus camera capable of performing the autofluorescence photographing, to perform the color photographing and the autofluorescence photographing, the filter needs to be switched. In addition, as illustrated in FIG. 4, an illumination optical system L1 and an observation photographing optical system L2 are disposed. In the illumination optical system L1, for example, a halogen light source 1 is used as an observation light source, and a xenon tube 2 is used as a photographing light source. The halogen light source 1 and the xenon tube 2 emit a light having wavelengths of a visible light and a near-infrared light.
When the autofluorescence photographing is performed, in the optical path of the illumination optical system L1, as an illumination system 1, an exciter filter 3 for transmitting only the excited light and a planar plate 4 for correcting an optical path length inserted at the time of color photographing are disposed to be insertable/removable.
In addition, in the observation photographing optical system L2, as a photographing system 1, a barrier filter 5, which is inserted at the time of fluorescence photographing and transmits only a light in a fluorescence wavelength band of the autofluorescence, and a near-infrared cut-off filter 6, which is inserted at the time of color photographing are disposed to be insertable/removable. The near-infrared cut-off filter 6 is used to prevent good image quality from deteriorating due to an excessive increase in red component of the color-photographed image.
In the aforementioned fundus camera, at the time of observation in the autofluorescence photographing mode, the exciter filter 3 needs to be inserted into the illumination system 1, the near-infrared cut-off filter 6 needs to be inserted into the photographing system 1, and the alignment and observation need to be performed through the finder. In addition, at the time of photographing, in the photographing system 1, the near-infrared cut-off filter 6 is replaced with the barrier filter 5, so that the photographing is performed.
In addition, at the time of observation and photographing in the color photographing mode, the planar plate 4 is inserted into the illumination system 1, and the near-infrared cut-off filter 6 is inserted into the photographing system 1. In addition, in the fundus camera, since the observation is performed by using the visible light, a mydriatic agent needs to be instilled into the eye of a person to be examined to obtain mydriasis.
In a second conventional fundus camera illustrated in FIG. 5, in the illumination optical system L1, a near-infrared light source 11 that emits a near-infrared light is used as an observation light source, and a xenon tube 12 that emits a light having wavelengths of a visible light and a near-infrared light is used as a photographing light source.
In the illumination optical system L1, as an illumination system 1, the near-infrared light cut-off filter 13 and the exciter filter 14 that transmits also the near-infrared light are disposed to be replaceable, and as an illumination system 2, the near-infrared light cut-off filter 15 and the planar plate 16 are disposed to be insertable/removable. In the observation photographing optical system L2, as a photographing system 1, in front of the image capture unit 17, the barrier filter 18 and the planar plate 19 are disposed to be replaceable. Therefore, the photographing in the color photographing mode and the fluorescence photographing mode can be performed.
As illustrated in FIG. 5, if one image capture unit is used, the image capture unit 17 needs to be configured to perform the observation by using the near-infrared light. At the time of still image photographing according to the second conventional fundus camera illustrated in FIG. 5, the infrared light cut-off filter needs to be inserted to the illumination optical system L1 or the observation photographing optical system L2.
Therefore, at the time of observation in the color photographing mode, the exciter filter 14 is inserted into the illumination system 1, the planar plate 16 is inserted into the illumination system 2, and the planar plate 19 is inserted into the photographing system 1, so that the observation is performed. In addition, at the time of photographing in the color photographing mode, the near-infrared light cut-off filter 13 is inserted into the illumination system 1, the planar plate 16 is inserted into the illumination system 2, and the planar plate 19 is inserted into the photographing system 1, so that the photographing is performed.
At the time of observation in the fluorescence photographing mode, the exciter filter 14 is inserted into the illumination system 1, the planar plate 16 is inserted into the illumination system 2, and the barrier filter 18 is inserted into the photographing system 1, so that the observation is performed. In addition, at the time of photographing in the fluorescence photographing mode, the exciter filter 14 is inserted into the illumination system 1, the near-infrared light cut-off filter 15 is inserted into the illumination system 2, and the barrier filter 18 is inserted into the photographing system 1, so that the photographing is performed.
As described above, to perform the photographing in the color photographing mode and the fluorescence photographing mode, three filter switching mechanisms are needed. The reason why the three switching mechanisms are needed is that, since the exciter filter 14 also transmits the infrared wavelength, the near-infrared light cut-off filters 13 and 15 for blocking the transmission of the infrared wavelength light are needed.
In a third conventional fundus camera illustrated in FIG. 6, two image capture units are provided to perform the color photographing and the autofluorescence photographing, and an illumination optical system L1 and observation photographing optical systems L2 and L3 are disposed. In the illumination optical system L1, for example, a halogen light source 21 is used as an observation light source, and a xenon tube 22 is used as a photographing light source. The halogen light source 21 and the xenon tube 22 emit a light having wavelengths of a visible light and a near-infrared light.
When the autofluorescence photographing is performed, in the optical path of the illumination optical system 1, as an illumination system 1, a exciter filter 23 for transmitting only the excited light and a planar plate 24 for correcting an optical path length inserted at the time of color photographing are disposed to be insertable.
In addition, in the observation photographing optical system L2, as a photographing system 1 a barrier filter 25, which is inserted at the time of fluorescence photographing and transmits only a light in a fluorescence wavelength band of the autofluorescence, and a planar plate 26, which is inserted at the time of color photographing and corrects an optical path length, are disposed to be insertable/removable. In addition, as a photographing system 2, a near-infrared light cut-off filter 28, which is needed to prevent good image quality from deteriorating due to an excessive increase in red component of the captured image, is disposed in front of a color-photographing image capture unit 27 of the observation photographing optical system L2. In an observation photographing optical system L3, which is branched by a switching mirror 29, an autofluorescence photographing image capture unit 30 is disposed.
In the fundus camera described above, at the time of observation in the autofluorescence photographing mode, a exciter filter 23 is inserted into the illumination system 1, a planar plate 26 is inserted into the photographing system 1, and alignment and observation are performed through a finder (not illustrated). In addition, at the time of photographing, in the photographing system 1, the planar plate 26 is replaced with the barrier filter 25, and the switching mirror 29 is inserted into the optical path, so that the photographing is performed by the image capture unit 30. In addition, at the time of observation and photographing in the color photographing mode, the planar plate 24 is inserted into the illumination system 1, and the switching mirror 29 recedes from the optical path, so that the photographing is performed by the image capture unit 27.
In addition, in the fundus camera described above, since the observation is performed by using the visible light, a mydriatic agent needs to be instilled into the eye of a person to be examined to obtain mydriasis.
The following Table 2 lists the examples of the conventional fundus cameras. In the Table, the symbol “NO” denotes that no filter exists at the corresponding position.
TABLE 2First conventional fundus camera(1)Photographing Mode --- Color/Autofluorescence(2)Observation Wavelength ---Visible Light(3)Color --- Fluorescence(4)Illumination System 1 Observation Time --- PlanarPlate/Exciter(5)Illumination System 1 Photographing Time --- PlanarPlate/Exciter(6)Illumination System 2 Observation Time --- NO/NO(7)Illumination System 2 Photographing Time --- NO/NO(8)Photographing System 1 Observation Time --- Near-InfraredLight Cut/Near-Infrared Light Cut(9)Photographing System 1 Photographing Time --- Near-InfraredLight Cut/Barrier(10)Photographing System 2 Observation Time --- NO/NOPhotographing System 2 Photographing Time --- NO/NOSecond conventional fundus camera(1)Photographing Mode --- Color/Visible Fluorescence(2)Observation Wavelength --- Near-Infrared Light(3)Color --- Fluorescence(4)Illumination System 1 Observation Time --- Exciter/Exciter(5)Illumination System 1 Photographing Time --- Near-InfraredLight Cut/Exciter(6)Illumination System 2 Observation Time --- Planar Plate/Planar Plate(7)Illumination System 2 Photographing Time --- PlanarPlate/Near-Infrared Light Cut(8)Photographing System 1 Observation Time --- PlanarPlate/Barrier(9)Photographing System 1 Photographing Time --- PlanarPlate/Barrier(10)Photographing System 2 Observation Time --- NO/NOPhotographing System 2 Photographing Time --- NO/NOThird conventional fundus camera(1)Photographing Mode --- Color/Autofluorescence(2)Observation Wavelength --- Visible Light(3)Color --- Fluorescence(4)Illumination System 1 Observation Time --- PlanarPlate/Exciter(5)Illumination System 1 Photographing Time --- PlanarPlate/Exciter(6)Illumination System 2 Observation Time --- NO/NO(7)Illumination System 2 Photographing Time --- NO/NO(8)Photographing System 1 Observation Time --- PlanarPlate/Planar Plate(9)Photographing System 1 Photographing Time --- PlanarPlate/Barrier(10)Photographing System 2 Observation Time --- Near-InfraredLight Cut/Near-Infrared Light Cut(11)Photographing System 2 Photographing Time ---Near-Infrared Light Cut --- Near-Infrared Light Cut
In this manner, in the first and third conventional fundus cameras where the autofluorescence photographing can be performed, since the mydriatic fundus camera is basically used, the observation is performed by using the visible light. Therefore, a person to be examined needs to be subjected to mydriasis. In addition, in the second conventional fundus camera, since the observation is performed by using the near-infrared light, three filter switching mechanisms are needed for the apparatus for performing the fluorescence photographing and the color photographing.